OpenSTA/search/Bfs.cc

// OpenSTA, Static Timing Analyzer
// Copyright (c) 2025, Parallax Software, Inc.
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// 
// The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software.
// 
// Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
// 
// This notice may not be removed or altered from any source distribution.

#include "Bfs.hh"

#include "Report.hh"
#include "Debug.hh"
#include "Mutex.hh"
#include "DispatchQueue.hh"
#include "Network.hh"
#include "Graph.hh"
#include "Sdc.hh"
#include "Levelize.hh"
#include "SearchPred.hh"

namespace sta {

BfsIterator::BfsIterator(BfsIndex bfs_index,
			 Level level_min,
			 Level level_max,
			 SearchPred *search_pred,
			 StaState *sta) :
  StaState(sta),
  bfs_index_(bfs_index),
  level_min_(level_min),
  level_max_(level_max),
  search_pred_(search_pred)
{
  init();
}

void
BfsIterator::init()
{
  first_level_ = level_max_;
  last_level_ = level_min_;
  ensureSize();
}

void
BfsIterator::ensureSize()
{
  if (levelize_->levelized()) {
    unsigned max_level_1 = levelize_->maxLevel() + 1;
    if (queue_.size() < max_level_1)
      queue_.resize(max_level_1);
  }
}

BfsIterator::~BfsIterator()
{
}

void
BfsIterator::clear()
{
  Level level = first_level_;
  while (levelLessOrEqual(level, last_level_)) {
    VertexSeq &level_vertices = queue_[level];
    for (Vertex *vertex : level_vertices) {
      if (vertex)
	vertex->setBfsInQueue(bfs_index_, false);
    }
    level_vertices.clear();
    incrLevel(level);
  }
  init();
}

void
BfsIterator::reportEntries()
{
  Level level = first_level_;
  while (levelLessOrEqual(level, last_level_)) {
    VertexSeq &level_vertices = queue_[level];
    if (!level_vertices.empty()) {
      report_->reportLine("Level %d", level);
      for (Vertex *vertex : level_vertices) {
	if (vertex)
	  report_->reportLine(" %s", vertex->to_string(this).c_str());
      }
    }
    incrLevel(level);
  }
}

void 
BfsIterator::deleteEntries(Level level)
{
  VertexSeq &level_vertices = queue_[level];
  for (Vertex *vertex : level_vertices) {
    if (vertex)
      vertex->setBfsInQueue(bfs_index_, false);
  }
  level_vertices.clear();
}

bool
BfsIterator::empty() const
{
  return levelLess(last_level_, first_level_);
}

void
BfsIterator::enqueueAdjacentVertices(Vertex *vertex)
{
  enqueueAdjacentVertices(vertex, search_pred_, level_max_);
}

void
BfsIterator::enqueueAdjacentVertices(Vertex *vertex,
				     SearchPred *search_pred)
{
  enqueueAdjacentVertices(vertex, search_pred, level_max_);
}

void
BfsIterator::enqueueAdjacentVertices(Vertex *vertex,
				     Level to_level)
{
  enqueueAdjacentVertices(vertex, search_pred_, to_level);
}

int
BfsIterator::visit(Level to_level,
		   VertexVisitor *visitor)
{
  int visit_count = 0;
  while (levelLessOrEqual(first_level_, last_level_)
	 && levelLessOrEqual(first_level_, to_level)) {
    VertexSeq &level_vertices = queue_[first_level_];
    incrLevel(first_level_);
    // Note that ArrivalVisitor::enqueueRefPinInputDelays may enqueue
    // vertices at this level so range iteration fails if the vector grows.
    while (!level_vertices.empty()) {
      Vertex *vertex = level_vertices.back();
      level_vertices.pop_back();
      if (vertex) {
        vertex->setBfsInQueue(bfs_index_, false);
        visitor->visit(vertex);
        visit_count++;
      }
    }
    level_vertices.clear();
    visitor->levelFinished();
  }
  return visit_count;
}

int
BfsIterator::visitParallel(Level to_level,
			   VertexVisitor *visitor)
{
  size_t thread_count = thread_count_;
  int visit_count = 0;
  if (!empty()) {
    if (thread_count == 1)
      visit_count = visit(to_level, visitor);
    else {
      std::vector<VertexVisitor*> visitors;
      for (int k = 0; k < thread_count_; k++)
	visitors.push_back(visitor->copy());
      while (levelLessOrEqual(first_level_, last_level_)
	     && levelLessOrEqual(first_level_, to_level)) {
	VertexSeq &level_vertices = queue_[first_level_];
	incrLevel(first_level_);
	if (!level_vertices.empty()) {
          size_t vertex_count = level_vertices.size();
          if (vertex_count < thread_count) {
            for (Vertex *vertex : level_vertices) {
              if (vertex) {
                vertex->setBfsInQueue(bfs_index_, false);
                visitor->visit(vertex);
              }
            }
          }
          else {
            size_t from = 0;
            size_t chunk_size = vertex_count / thread_count;
            BfsIndex bfs_index = bfs_index_;
            for (size_t k = 0; k < thread_count; k++) {
              // Last thread gets the left overs.
              size_t to = (k == thread_count - 1) ? vertex_count : from + chunk_size;
              dispatch_queue_->dispatch( [=](int) {
                for (size_t i = from; i < to; i++) {
                  Vertex *vertex = level_vertices[i];
                  if (vertex) {
                    vertex->setBfsInQueue(bfs_index, false);
                    visitors[k]->visit(vertex);
                  }
                }
              });
              from = to;
            }
            dispatch_queue_->finishTasks();
          }
	  visitor->levelFinished();
	  level_vertices.clear();
	}
      }
      for (VertexVisitor *visitor : visitors)
	delete visitor;
    }
  }
  return visit_count;
}

bool
BfsIterator::hasNext()
{
  return hasNext(last_level_);
}

bool
BfsIterator::hasNext(Level to_level)
{
  findNext(to_level);
  return levelLessOrEqual(first_level_, last_level_)
     && !queue_[first_level_].empty();
}

Vertex *
BfsIterator::next()
{
  VertexSeq &level_vertices = queue_[first_level_];
  Vertex *vertex = level_vertices.back();
  level_vertices.pop_back();
  vertex->setBfsInQueue(bfs_index_, false);
  return vertex;
}

void
BfsIterator::findNext(Level to_level)
{
  while (levelLessOrEqual(first_level_, last_level_)
	 && levelLessOrEqual(first_level_, to_level)
	 && queue_[first_level_].empty())
    incrLevel(first_level_);
}

void
BfsIterator::enqueue(Vertex *vertex)
{
  debugPrint(debug_, "bfs", 2, "enqueue %s",
             vertex->to_string(this).c_str());
  if (!vertex->bfsInQueue(bfs_index_)) {
    Level level = vertex->level();
    LockGuard lock(queue_lock_);
    if (!vertex->bfsInQueue(bfs_index_)) {
      vertex->setBfsInQueue(bfs_index_, true);
      queue_[level].push_back(vertex);

      if (levelLess(last_level_, level))
	last_level_ = level;
      if (levelLess(level, first_level_))
	first_level_ = level;
    }
  }
}

bool
BfsIterator::inQueue(Vertex *vertex)
{
  //  checkInQueue(vertex);
  return vertex->bfsInQueue(bfs_index_);
}

void
BfsIterator::checkInQueue(Vertex *vertex)
{
  Level level = vertex->level();
  if (static_cast<Level>(queue_.size()) > level) {
    for (Vertex *v : queue_[level]) {
      if (v == vertex) {
	if (vertex->bfsInQueue(bfs_index_))
	  return;
	else
	  printf("extra %s\n", vertex->to_string(this).c_str());
      }
    }
  }
  if (vertex->bfsInQueue(bfs_index_))
    printf("missing %s\n", vertex->to_string(this).c_str());
}

void
BfsIterator::deleteVertexBefore(Vertex *vertex)
{
  remove(vertex);
}

// Remove by inserting null vertex pointer.
void
BfsIterator::remove(Vertex *vertex)
{
  // If the iterator has not been inited the queue will be empty.
  Level level = vertex->level();
  if (vertex->bfsInQueue(bfs_index_)
      && static_cast<Level>(queue_.size()) > level) {
    for (Vertex *&v : queue_[level]) {
      if (v == vertex) {
	v = nullptr;
	vertex->setBfsInQueue(bfs_index_, false);
        break;
      }
    }
  }
}

////////////////////////////////////////////////////////////////

BfsFwdIterator::BfsFwdIterator(BfsIndex bfs_index,
			       SearchPred *search_pred,
			       StaState *sta) :
  BfsIterator(bfs_index, 0, level_max, search_pred, sta)
{
}

// clear() without saving lists to list_free_.
BfsFwdIterator::~BfsFwdIterator()
{
  for (Level level = first_level_; level <= last_level_; level++)
    deleteEntries(level);
}

void
BfsFwdIterator::incrLevel(Level &level)
{
  level++;
}

bool
BfsFwdIterator::levelLessOrEqual(Level level1,
				 Level level2) const
{
  return level1 <= level2;
}

bool
BfsFwdIterator::levelLess(Level level1,
			  Level level2) const
{
  return level1 < level2;
}

void
BfsFwdIterator::enqueueAdjacentVertices(Vertex *vertex,
					SearchPred *search_pred,
					Level to_level)
{
  if (search_pred->searchFrom(vertex)) {
    VertexOutEdgeIterator edge_iter(vertex, graph_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      Vertex *to_vertex = edge->to(graph_);
      if (to_vertex->level() <= to_level
	  && search_pred->searchThru(edge)
	  && search_pred->searchTo(to_vertex))
	enqueue(to_vertex);
    }
  }
}

////////////////////////////////////////////////////////////////

BfsBkwdIterator::BfsBkwdIterator(BfsIndex bfs_index,
				 SearchPred *search_pred,
				 StaState *sta) :
  BfsIterator(bfs_index, level_max, 0, search_pred, sta)
{
}

// clear() without saving lists to list_free_.
BfsBkwdIterator::~BfsBkwdIterator()
{
  for (Level level = first_level_; level >= last_level_; level--)
    deleteEntries(level);
}

void
BfsBkwdIterator::incrLevel(Level &level)
{
  level--;
}

bool
BfsBkwdIterator::levelLessOrEqual(Level level1,
				  Level level2) const
{
  return level1 >= level2;
}

bool
BfsBkwdIterator::levelLess(Level level1,
			   Level level2) const
{
  return level1 > level2;
}

void
BfsBkwdIterator::enqueueAdjacentVertices(Vertex *vertex,
					 SearchPred *search_pred,
					 Level to_level)
{
  if (search_pred->searchTo(vertex)) {
    VertexInEdgeIterator edge_iter(vertex, graph_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      Vertex *from_vertex = edge->from(graph_);
      if (from_vertex->level() >= to_level
	  && search_pred->searchFrom(from_vertex)
	  && search_pred->searchThru(edge))
	enqueue(from_vertex);
    }
  }
}

} // namespace